The present invention relates to a method of controlling ignition timing of an internal combustion engine by using an electronic ignition control system.
According to an ignition timing control method using an electronic ignition timing control apparatus, the operating condition of an internal combustion engine is detected by various sensors, and then, the optimum ignition timing is calculated based on detection signals from the various sensors by using a predetermined algorithm. In such method, the operating condition of an engine is generally detected by measuring the amount of air sucked into the engine and the rotational speed of the engine, or by measuring the vacuum level in an intake manifold of the engine and the rotational speed of the engine. Then, the ignition timing is controlled in such a manner that it is advanced, in other words, the spark-advance angle is controlled in such a manner that it is increased, when the rotational speed increases, and the ignition timing is controlled in such a manner that it is delayed, in other words, the spark-advance angle is controlled in such a manner that it is decreased, when the rotational speed decreases. Furthermore, the ignition timing is controlled in such a manner that it is delayed when the amount of air sucked into the engine increases or when the vacuum level decreases, and the ignition timing is controlled in such a manner that it is advanced when the amount of sucked air decreases or when the vacuum level increases.
However, when a conventional engine adopting the above-mentioned ignition timing control method is rapidly accelerated, since the amount of air sucked into the engine or the vacuum level in the intake manifold greatly increases or decreases, for a moment, the ignition timing is controlled in such a manner that it is excessively delayed. Particularly when the engine is rotating at a low speed, since the ignition timing changes greatly compared with the amount of change in the air sucked into the engine or in the vacuum level in the intake manifold of the engine, the above-mentioned tendency is extremely great. As a result, according to a conventional ignition timing control method, a quick increase of engine torque cannot be obtained during an accelerating operation. In other words, the accelerating characteristics are extremely poor in the conventional engine.